Carbon Sequestration by Potassium-Modified Bagasse Biochar in Manganese-Contaminated Sugarcane Field Soils

This study aims to investigate the transformation and carbon sequestration mechanisms of soil organic carbon in manganese-contaminated farmland. A 100-day constant temperature incubation experiment was conducted using potassium dihydrogen phosphate-modified bagasse biochar (BC-K) at concentrations of 0%, 0.5%, 2%, and 5%. The effects of BC-K on the mineralization of organic carbon and the changes in the physicochemical properties of manganese-contaminated soils were examined. The results demonstrated that applying 0.5%, 2%, and 5% BC-K to manganese-contaminated soils significantly reduced cumulative CO₂ emissions by 411.94 mg·kg^− 1, 47.33 mg·kg^− 1, and 105.24 mg·kg^− 1, respectively. The greatest reduction was observed with the 0.5% BC-K application compared to the control. The application of 2% and 5% BC-K to manganese-contaminated soil increased SOC by 121.50–165.23%, DOC by 24.46–30.05%, and MBC by 5.41 to 6.19 times. However, ROC decreased by 29.83–30.04%. In addition, the application of BC-K in manganese-contaminated soil can increase soil AP, AK, CEC, pH, and catalase. The application of BC-K can effectively reduce CO₂ emissions in manganese-contaminated farmland soil while significantly increasing soil organic carbon content and improving its physical and chemical properties. The findings of this study offer a scientific foundation for developing carbon sequestration and soil nutrient management strategies in manganese-contaminated farmland soils. These insights are crucial for enhancing soil environmental quality.